In processes for the cold working or forming of iron and steel materials, it is well known in the art to apply a lubricant composition to the metal surface to be deformed in order to eliminate, or at least minimize, the friction between the material to be processed and the metal working tool or die. Typically, where only simple deformation or forming is involved, the desired lubrication has been provided by the application of oils to the metal surface, which oils may be emulsified and/or contain one or more additives to improve the lubricity of the oil during the forming operation. Where more severe metal forming or deformation is involved, it has been customary to provide, on the surface of the metal to be deformed, a zinc phosphate film hopeite) or a mixed film of zinc phosphate and zinc iron phosphate (phosphophyllite) as the base layer to which is applied a fatty acid soap lubricant composition, such as a sodium stearate or zinc stearate soap.
In recent years, as the shape of the cold formed articles have become more complex and the hardness of the iron and steel materials to be deformed has increased, the cold forming operations have become increasingly severe with the result that even where lubricant films utilizing the prior art phosphate coatings have been employed, problems of coining and/or stick-slip phenomena have been frequently encountered. For example, in cold forging processes, the degree of cold working per process, i.e., the cross section reduction ratio, has reached 80%, with the result that the surface temperatures of the material being processed rises to 300.degree. C. and higher. This has frequently resulted in the thermal decomposition or even physical destruction of the prior art phosphate films during the cold forming operation.
In an attempt to overcome these problems, lubricant materials having good heat resistance, such as molybdenum disulphide and graphite have been used, either alone or in combination with a phosphate film. These materials, when used alone, have been found to have poor adhesion to the surface of the iron or steel material to be deformed and, hence, have not produced satisfactory results. Even when used in combination with a phosphate film, due to the thermal decomposition or physical destruction of this film during the forming operation, the combination has not provided any significant improvement.
The problems described above have also begun to be encountered in processes for the cold drawing of iron or steel pipe and wire, although such processes have not heretofore been considered to involve the high degrees of deformation as in a cold forming process. This has been caused by an increase in the speed at which the drawing operation has been carried out and by the use of harder, less malleable iron and steel materials. The result has been a significant increase in the severity of the working which has been accompanied by problems of scorching, and severe tool friction, which has resulted in a significant decrease in tool life and an increase in tool cost.
It is, therefore, an object of the present invention to provide an improved process for the cold forming or working of iron and steel materials.
A further object of the present invention is to provide an improved lubricant system, by the use of which the aforementioned problems in present cold forming operations will be greatly minimized, if not overcome.
These and other objects will become apparent to those of ordinary skill in the art from the description of the invention which follows: